Fairing for folding wing tip

ABSTRACT

An aircraft with wing tip devices, for example, folding wing tips, is disclosed. The folding wing tip may have a flight configuration for use during flight, and a ground configuration for use in ground-based operations. The ground configuration creates a shorter wing span than when the aircraft is in the flight configuration. A hinge arrangement protrudes beyond an outer surface of the fixed wing and wing tip device. In order to reduce the aerodynamic effect of the protruding hinge a fairing may be provided. In the flight configuration the fairing comprises a rear portion with a concave surface, such that the fairing acts as a lift-generating surface when the aircraft is in flight.

BACKGROUND OF THE INVENTION

There is a trend towards increasingly large passenger aircraft, forwhich it is desirable to have correspondingly large wing spans. However,the maximum aircraft span is effectively limited by airport operatingrules which govern various clearances required when manoeuvring aroundthe airport (such as the span and/or ground clearance required for gateentry and safe taxiway usage).

Therefore, folding wing tip devices have been introduced into passengeraircraft, where a wing tip device is movable between a flightconfiguration for use during flight, and a ground configuration for useduring ground-based operations. In the ground configuration, the wingtip device is moved away from the flight configuration such that thespan of the aircraft wing is reduced, thereby allowing use of existinggates and safe taxiway usage.

The folding wing tip device may be connected to a fixed wing via a hingearrangement. The hinge arrangement may protrude beyond the wing skin ofthe fixed wing and wing tip device, resulting in a need for a fairing tocover the exposed section of the hinge arrangement in order that theaerodynamic performance of the wing is not adversely affected. Variousshapes of fairings are already known on an aircraft, for example blisterfairings or flap track fairings. However, locating already-known shapesof fairing at the junction between the folding wing tip device and fixedwing have been found to result in an undesirable degree of lift lossand/or additional drag, when compared to a non-folding wing of the samespan.

The present invention seeks to mitigate the above-mentioned problems.Alternatively or additionally, the present invention seeks to provide animproved fairing to reduce or eliminate the impact on lift loss at ajunction between a fixed wing and wing tip device.

SUMMARY OF THE INVENTION

The present invention provides an aircraft comprising an aircraft wing,the aircraft wing comprising a fixed wing and a wing tip device at thetip thereof, wherein the wing tip device is configurable between: (i) aflight configuration for use during flight and (ii) a groundconfiguration for use during ground-based operations, in which groundconfiguration the wing tip device is moved away from the flightconfiguration such that the span of the aircraft wing is reduced, theaircraft wing further comprising a hinge arrangement connecting thefixed wing and the wing tip device, wherein the hinge arrangementprotrudes beyond an outer surface of the fixed wing and wing tip device,and a fairing covering the protruding portion of the hinge, wherein inthe flight configuration the fairing comprises a rear portion with aconcave surface, the surface creating a lift-generating portion of thefairing during flight.

Shaping the fairing such that a portion acts as a lift-generatingportion during flight may eliminate or reduce the lift loss typicallyassociated with the placement of a fairing on an aircraft wing.

The rear portion may comprise a trailing edge with a width in thespan-wise direction. The rear portion may extend beyond the trailingedge of the fixed wing and wing tip device. The rear portion of thefairing may comprise a trailing edge which is parallel to the trailingedge of the fixed wing and/or wing tip device. The rear portion maytaper in span-wise width as it extends away from the trailing edge ofthe fixed wing and wing tip device.

The rear portion may comprise a point of inflection in the line offlight direction, at which point the cross-sectional profile of the rearportion in the line of flight direction changes from a convex profile toa concave profile, as the rear portion extends in a rearward direction.The point of inflection may be located in a region around 100%, 90%,80%, 70%, or 60% of the chord length of the wing, taken in a line offlight direction and moving from the leading edge (0%) to trailing edge(100%) of the wing. The line of flight direction is taken along thelongitudinal axis of the aircraft. The span-wise direction is taken tobe perpendicular to the line of flight direction.

The aircraft may be arranged such that as the fairing extends in aspan-wise direction, the rear portion of the fairing comprises a surfacewhich extends substantially tangentially from the wing skin of the fixedwing in a concave direction, undergoes a point of inflection to extendin a convex direction, and undergoes a further point of inflection suchthat it extends in a concave direction to a point where it issubstantially tangential to the wing skin of the wing tip device. Thisbell-shaped cross-section may reduce in depth as the rear portionextends rearwardly, such that at the trailing edge of the fairing, thebell-shaped cross-section is much reduced or eliminated (i.e. flat) in aspan-wise direction. As previously, such definitions are when the wingtip device is in the flight configuration. The aircraft may comprise oneor more seals where the fairing meets the fixed wing and/or the wing tipdevice.

The fairing may comprise a front portion blended into and extendingrearwardly from the leading edge of the fixed wing and the wing tipdevice when the wing tip device is in the flight configuration.

Provision of a fairing with a front portion blended into the leadingedge of the fixed wing and wing tip device may reduce or eliminate thelift loss experienced by an aircraft wing where the fixed wing and wingtip device meet. As such, the aerodynamic performance of the wing may beimproved.

The blending of the fairing into the leading edge of the fixed wing andwing tip device means that there are no discontinuities between thefairing and the leading edge of the fixed wing and wing tip device. Thisblending is in all directions, so tracing a line across the fairing andthe leading edge of the fixed wing and wing tip device in a span-wisedirection, a smooth transition is provided. Equally, tracing a linebackwards from the leading edge of the fixed wing and wing tip device ina line of flight direction, a smooth transition is provided. The frontportion of the fairing may be considered as aerodynamically seamlesswhere it blends with the leading edge of the wing, such that the shapeof the fairing results in no separation or stagnation points beingcreated by the front portion of the fairing when the aircraft is inflight. There may be a line of continuous curvature extending from thefront portion of the fairing around the leading edge of the wing. Theline of continuous curvature may extend around the fairing and the wingin a line-of-flight direction. There may be a multiplicity of lines ofcontinuous curvature, spaced across the width of the fairing, and eachextending from the front portion of the fairing around the leading edgeof the wing.

The fairing may be shaped such that the depth of the fairing is greatestto correspond with the maximum protrusion of the hinge arrangement. Inorder to provide a smooth transition between the fairing and the fixedwing and wing tip device in a span-wise direction, the fairing maycomprise a concave surface from the wing skin of the fixed wing, theconcave surface starting in a direction tangential to the wing skin. Thefairing may further comprise a point of inflection in a span-wisedirection, at which point the surface becomes a convex surface. Theconvex surface may peak to correspond to the maximum protrusion of thehinge arrangement. The fairing may further comprise an additional pointof inflection, at which point the surface becomes a concave surface,such that the concave surface meets the wing tip device wing skin in atangential direction. This applies when the wing tip device is in theflight configuration, not necessarily when the wing tip device is in theground configuration. An alternative way of describing the span-wisecross-sectional profile of the front portion is that is traces abell-shaped profile. At the very leading edge of the front portion, thebell-shaped profile may be very small, or non-existent (i.e. flat)because the fairing blends with the leading edge of the wing, but as thefront portion extends rearwardly from the leading edge, the depth of thebell-shaped profile may increase. The aircraft may comprise one or moreseals where the fairing meets the fixed wing and/or the wing tip device.

The fairing may be substantially symmetrical about an axial planerunning along the line of flight direction and normal to the wingdihedral, the axis located at the point of greatest depth of thefairing. The fairing may be symmetrical about such a line of flight axisalong at least 70%, 80% or 90% of the axis. If the wing is a swept wing,the very front of the front portion of the fairing may deviate fromsymmetry due to the angle created between the leading edge of the fixedwing and wing tip device and the axis. If the wing is a swept wing, arear portion of the fairing may deviate from symmetry due to the anglecreated by the trailing edge of the fairing and the axis.

The edges of the fairing, where the fairing blends into the fixed wingor wing tip device may extend in a line of flight direction. As such,the fairing may have a consistent width in a span-wise direction. Suchan arrangement may reduce lift loss.

The front portion of the fairing may meet the leading edge of the fixedwing and wing tip device in a tangential direction, such that whenviewed in a line of flight cross-section, there is no discontinuitybetween the fairing, the leading edge of the fixed wing and wing tipdevice.

The hinge arrangement may extend in a line of flight direction. Thehinge arrangement may extend in a line of flight direction such that itextends over at least 60%, at least 70%, at least 80%, or at least 90%of the chord of the aircraft wing in a line of flight direction (i.e.between the leading edge of the wing and the trailing edge of the wingin a line of flight direction). As a result, the hinge arrangement mayprotrude from at or near the leading edge of the fixed wing and wing tipdevice. The present invention provides a fairing which enables the hingearrangement in such an aircraft wing to be covered without it beingnecessary to extend the fairing beyond the leading edge of the aircraftwing. Such an arrangement may be advantageous aerodynamically.

The fairing may be located on the lower surface of the aircraft wing.The lower surface of the aircraft wing is defined as the surface of thewing which faces the ground when the aircraft is on the ground. In analternative arrangement, the fairing may be located on the upper surfaceof the wing. The determination of the surface with which to associatethe fairing may depend on the surface from which the hinge arrangementprotrudes.

According to a second aspect, the invention provides an aircraft wingcomprising a fixed wing and a wing tip device at the tip thereof,wherein the wing tip device is configurable between: (i) a flightconfiguration for use during flight and (ii) a ground configuration foruse during ground-based operations, in which ground configuration thewing tip device is moved away from the flight configuration such thatthe span of the aircraft wing is reduced, the aircraft wing furthercomprising a hinge arrangement connecting the fixed wing and the wingtip device, wherein the hinge arrangement protrudes beyond an outersurface of the fixed wing and wing tip device, and a fairing coveringthe protruding portion of the hinge, wherein in the flight configurationthe fairing comprises a rear portion, with a concave surface, thesurface creating a lift-generating portion of the fairing during flight.

According to a third aspect of the invention, there is provided anaircraft comprising an aerodynamic structure and a fairing, wherein thefairing is blended into the aerodynamic structure in a line of flightdirection and a span-wise direction, such that there are nodiscontinuities in the transition from the aerodynamic structure and thefairing. The fairing may comprise a point of inflection in a line offlight direction. Such a point of inflection may improve the aerodynamicperformance of the fairing. The fairing may comprise an under camber.The fairing may add to the lift created by the aerodynamic structure.

According to a fourth aspect, the invention provides a fairing for anaircraft, the fairing comprising an interface surface for interfacingwith the aircraft in a tangential direction, and an aerodynamic surface,the fairing further comprising a seamless transition from the interfacesurface to the aerodynamic surface.

The fairing may comprise a longitudinal axis corresponding to the lineof flight direction when mounted on an aircraft, wherein thecross-sectional profile of the fairing taken perpendicular to thelongitudinal axis comprises a bell-shaped curve. The aerodynamic surfacemay comprise a concave surface, for example, an under camber.

In embodiments of the present invention, the wing tip device isconfigurable between: (a) a flight configuration for use during flightand (b) a ground configuration for use during ground-based operations,in which ground configuration the wing tip device is moved away from theflight configuration such that the span of the aircraft wing is reduced.In the flight configuration, the span may exceed an airportcompatibility limit. In the ground configuration the span may be reducedsuch that the span (with the wing tip device in the groundconfiguration) is less than, or substantially equal to, the airportcompatibility limit. The airport compatibility limit is a span limit(for example relating to clearance restrictions for buildings, signs,other aircraft). The compatibility limit is preferably a gate limit.

The wing tip device may be a wing tip extension; for example the wingtip device may be a planar tip extension. In other embodiments, the wingtip device may comprise, or consist of, a non-planar device, such as awinglet.

In the flight configuration the trailing edge of the wing tip device ispreferably a continuation of the trailing edge of the fixed wing. Theleading edge of the wing tip device is preferably a continuation of theleading edge of the fixed wing. There is preferably a smooth transitionfrom the fixed wing to the wing tip device. It will be appreciated thatthere may be a smooth transition, even where there are changes in sweepor twist at the junction between the fixed wing and wing tip device.However, there are preferably no discontinuities at the junction betweenthe fixed wing and wing tip device. The upper and the lower surfaces ofthe wing tip device may be continuations of the upper and lower surfacesof the fixed wing. The span ratio of the fixed wing relative to the wingtip device may be such that the fixed wing comprises at least 70%, 80%,90%, or more, of the overall span of the aircraft wing.

When the wing tip device is in the ground configuration, the aircraftincorporating the wing, may be unsuitable for flight. For example, thewing tip device may be aerodynamically and/or structurally unsuitablefor flight in the ground configuration. The aircraft is preferablyconfigured such that, during flight, the wing tip device is not moveableto the ground configuration. The aircraft may comprise a sensor forsensing when the aircraft is in flight. When the sensor senses that theaircraft is in flight, a control system is preferably arranged todisable the possibility of moving the wing tip device to the groundconfiguration.

The aircraft is preferably a passenger aircraft. The passenger aircraftpreferably comprises a passenger cabin comprising a plurality of rowsand columns of seat units for accommodating a multiplicity ofpassengers. The aircraft may have a capacity of at least 20, morepreferably at least 50 passengers, and more preferably more than 50passengers. The aircraft is preferably a powered aircraft. The aircraftpreferably comprises an engine for propelling the aircraft. The aircraftmay comprise wing-mounted, and preferably underwing, engines.

It will of course be appreciated that features described in relation toone aspect of the present invention may be incorporated into otheraspects of the present invention. For example, the method of theinvention may incorporate any of the features described with referenceto the apparatus of the invention and vice versa.

The term ‘or’ shall be interpreted as ‘and/or’ unless the contextrequires otherwise.

DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample only with reference to the accompanying schematic drawings ofwhich:

FIG. 1 shows an aircraft wing comprising a wing tip device and fixedwing according to an embodiment of the invention;

FIG. 2 shows an aircraft comprising an aircraft wing as shown in FIG. 1;

FIG. 3 is a schematic view of a fairing on the underside of an aircraftwing according to an embodiment of the invention

FIG. 4 is a plan view of the underside of the embodiment shown in FIG.3;

FIG. 5 is a view of the underside of an aircraft wing and fairing,similar to FIG. 4, along with some span-wise cross-sectional profiles ofthe fairing;

FIG. 6 is a schematic view of a slice of the wing of FIG. 3 taken in aspan-wise direction

FIG. 7 is a cross-sectional view in a line of flight direction of theaircraft wing and fairing shown in FIG. 3;

FIG. 8 is a schematic view of a fairing on a wing according to a secondembodiment of the invention;

FIG. 9 is a plan view of the underside of the wing shown in FIG. 8;

FIG. 10 is a schematic view of the wing as shown in FIG. 3, with a pointof inflection clearly indicated;

FIG. 11 is a graph showing the aerodynamic portion of a wing withalternative fairings including a fairing according to the invention; and

FIG. 12 is an enlarged section of the graph shown in FIG. 11.

DETAILED DESCRIPTION

FIG. 1 shows an aircraft wing 10 comprising a wing tip device 12 and afixed wing 14. In FIG. 1 the wing tip device 12 is in a groundconfiguration in which the span of the aircraft wing 10 is reducedcompared to a flight configuration. FIG. 2 shows the aircraft wing 10 ofFIG. 1 as part of an aircraft 100. In FIG. 2, the aircraft wing 100 isin the flight configuration, where the wing tip device 12 has beenextended from the ground configuration shown in FIG. 1.

FIGS. 3 and 4 show an enlarged schematic view of the wing tip device 12,fixed wing 14, and a fairing 18 which extends from the wing tip device12 to the fixed wing 14 when the aircraft is in the flightconfiguration.

FIG. 6 shows a cross-sectional slice of a middle section of the wing 10in a span-wise direction. The wing tip device 12 is connected to thefixed wing 14 via a hinge arrangement 16. The hinge arrangement 16extends from a position at or close to the leading edge of the wing 10to a position at or close to the trailing edge of the wing 10. Variousdifferent hinge arrangements may be suitable, and the protrudingstructure may take a number of forms depending on the design of thehinge arrangement. For example the hinge may include lugs, lockingmechanisms, and/or actuation mechanisms, at least part of which mayprotrude from the wing outer mould line (OML). In most cases it isexpected that at least part of the hinge arrangement for a folding wingtip. would protrude from the OML at a location relatively far forward onthe wing (i.e. relatively close to the leading edge). The hingearrangement 16 allows the folding upwards, along a hinge line 22, of thewing tip device 12 from the flight configuration shown in FIG. 2 to theground configuration shown in FIG. 1. The folding of the wing tip devicebetween the flight configuration and ground configuration is controlledby an actuator (not shown) which may form part of the hinge arrangement16. The skilled person will appreciate that various different actuatorsand actuation methods may be used, and no further details are required.The hinge arrangement 16 may also comprise a locking mechanism arrangedto lock the folding wing tip device into the flight configuration.Various different locking mechanism may be suitable, as would beunderstood by a skilled person. As such, no further details will beprovided. As can be seen, the hinge arrangement 16 extends outside thewing skin envelope of the fixed wing 14 and the folding wing tip 12, inparticular extending from the underside of the wing 10.

FIG. 7 shows an second cross-sectional view of the arrangement of FIG.6, the cross-sectional view taken in the line of flight direction andthrough the hinge line 22. The outer surface of the fairing 18 isrepresented by a dashed line, which extends beyond the lower wing skinof the fixed wing 14 and wing tip device 12 to cover the hinge 16.Further details about the shape of the fairing are provided below

FIG. 5 shows the underside of the wing 10 and fairing 18 which coversthe hinge arrangement 16. The fairing 18 comprises a front portion 20which is blended into and extends rearwardly from the leading edge 23 ofthe fixed wing 14 and wing tip device 12. In this embodiment, the hingearrangement 16 comprises a hinge line 22 which is aligned with the lineof flight direction. The fairing 18 is also aligned with the line offlight direction and approximately symmetrical about the hinge axis 22.The span-wise edges of the fairing also extend in a line of flightdirection, such that the span-wise width of the fairing is consistent.Providing parallel, line of flight oriented, edges to the fairing 16acts to maintain lift due to the existence of the fairing, giving acontinuity of span loading.

The blending of the front portion 20 of the fairing 18 into the leadingedge 23 of the fixed wing 14 and folding wing tip device 12 means that,when looking a cross section of the wing profile in the line of flightdirection (as in FIG. 7), there are no discontinuities or abrupt edgesas the profile is traced from the leading edge 23 towards the trailingedge of the wing 10. As shown in FIG. 7, a line traced from the uppersurface of the wing 10, around the leading edge 23, and rearwards alongthe front portion of the fairing has a continuous curvature. Whilst thedepth of the fairing will vary across the width of the fairing, thecontinuous curvature in the line of flight direction remains, therebyacross the whole width of the fairing and wing an effective aerofoilprofile is provided at the leading edge 23 of the wing 10. This can beseen clearly in FIGS. 3 and 7. A continuous curvature is also providedwhen considering the lateral (i.e. span-wise) extension of the fairing18 from the fixed wing 14 to the folding wing tip device 12. There areno discontinuities or abrupt edges as the fairing extends in a span-wisedirection at the leading edge 23 of the wing 10. This smoothnesscontinues as the fairing 18 extends away from the leading edge of thewing 10 towards the trailing edge of the wing 10. The cross sectionalshape traced by the fairing 18 in the span-wise direction is bellshaped, so the fairing 18 initially extends from the wing skin of thefixed wing 14 in a concave manner, undergoes a point of inflection andextends in a convex manner as it extends around the hinge arrangement16, undergoes a further point of inflection and extends in a concavemanner to the wing skin of the folded wing tip device 12. At the pointwhere the fairing 18 meets the wing skin of the fixed wing 14 andfolding wing tip device 12, the fairing 18 extends substantiallytangentially to the wing skin. This profile change can be seen in FIG.5, where cross-sections of the fairing taken along the lines A-A, B-B,and C-C, are indicated. The bell shaped curve increases in depth fromA-A to B-B and then decreases in depth from B-B to C-C. The increase anddecrease in depth is done gradually, so no discontinuities exist on theexterior surface of the fairing 18. Whilst not shown in the figures, theskilled person will appreciate that seals may be provided at theinterface between the wing skin and the fairing, particularly at theinterface between the wing skin of the wing tip device and the fairing.

As shown in FIG. 5, the fairing 18 also comprises a rear portion 24,which extends beyond the trailing edge of the fixed wing 14 and foldingwing tip device 12 in a rearward direction. The rear portion 24 tapersin width as it extends beyond the trailing edge of the fixed wing 14 andfolding wing tip device 12. As shown in FIG. 5, the rear portion 24comprises a trailing edge 26, which is approximately aligned with thetrailing edge of the fixed wing 14 and folding wing tip device 12. Whenlooking at a cross sectional view of the middle of the fairing 18 in theline of flight direction (as in FIG. 7), as the fairing 18 extends fromthe front portion 20 to the rear portion 24 it first traces a convexpath until it reaches a point of inflection 21 and then traces a concavepath until it reaches the trailing edge 26. This point of inflection 21towards the rear of the fairing creates a concave surface and results inthe fairing 18 becoming a lift creating aerodynamic surface. The pointof inflection 21 is located around the 100%, 90%, 80%, 70%, or 60% ofthe chord length of the wing 10, taken in a line of flight direction andmoving from the leading edge (0%) to trailing edge (100%) of the wing.In certain embodiments, when the fairing extends far enough beyond thetrailing edge of the wing 10, the point of inflection 21 may be locatedaround 110%, 120% or more of the chord length of the wing. The exactlocation of the point of inflection 21 may depend on the particular wingand hinge configuration, and be determined experimentally, by testinghow the variation in location affects the lift loss experienced as aresult of introduction of the fairing 18. FIG. 10 shows athree-dimensional representation of the fairing (similar to FIG. 3) withthe point of inflection 21 clearly indicated with a line showing how thesurface changes direction.

FIGS. 8 and 9 show a similar fairing and wing arrangement to that shownin FIGS. 3 to 7, and 10. A wing tip device 12′ and a fixed wing 14′ arejoined by a hinge (not shown) and a fairing 18′ covers the hinge whereit protrudes from the OML of the wing. The front portion of the fairing18′ is the same shape as in the first embodiment described. The rearportion of the fairing 18′ is the same shape as in the first embodimentdescribed, in that the rear portion comprises a surface which creates aconcave surface. However, the fairing 18′ does not extend beyond thetrailing edge of the wing 10′. Such an arrangement may be possible whenthe protrusion of the hinge joining the fixed wing 14′ and the wing tipdevice 12′ is reduced either in depth or in the line of flightdirection.

FIG. 11 shows a schematic representation of a graph showing the liftcharacteristics of a wing as it extends in a span-wise direction. Thehinge line and the wing tip are indicated on the span axis of the graph.FIG. 12 shows an expanded section 600 of the graph shown in FIG. 11. Itcan be seen that conventional fairings, as indicated by the lines 606,for example blister shaped fairings, result in lift loss in the part ofthe wing to which they are attached. However, the blended fairing, asdescribed above, is lift-neutral when compared to a fixed wing with nowing tip device and associated fairing. The lift characteristics of awing without a fairing is shown by line 602 and the lift characteristicsof the wing according to an embodiment of the invention is shown by line604. Therefore, it can be seen the present invention offers significantadvantages of the existing fairing designs.

Whilst the present invention has been described and illustrated withreference to particular embodiments, it will be appreciated by those ofordinary skill in the art that the invention lends itself to manydifferent variations not specifically illustrated herein.

Where in the foregoing description, integers or elements are mentionedwhich have known, obvious or foreseeable equivalents, then suchequivalents are herein incorporated as if individually set forth.Reference should be made to the claims for determining the true scope ofthe present invention, which should be construed so as to encompass anysuch equivalents. It will also be appreciated by the reader thatintegers or features of the invention that are described as preferable,advantageous, convenient or the like are optional and do not limit thescope of the independent claims. Moreover, it is to be understood thatsuch optional integers or features, whilst of possible benefit in someembodiments of the invention, may not be desirable, and may therefore beabsent, in other embodiments.

1. An aircraft comprising an aircraft wing, the aircraft wing comprisinga fixed wing and a wing tip device at the tip thereof, wherein the wingtip device is configurable between: (i) a flight configuration for useduring flight and (ii) a ground configuration for use duringground-based operations, in which ground configuration the wing tipdevice is moved away from the flight configuration such that the span ofthe aircraft wing is reduced, the aircraft wing further comprising ahinge arrangement connecting the fixed wing and the wing tip device,wherein the hinge arrangement protrudes beyond an outer surface of thefixed wing and wing tip device, and a fairing covering the protrudingportion of the hinge, wherein the fairing comprises a rear portion witha concave surface, the surface creating a lift-generating portion of thefairing during flight.
 2. An aircraft as claimed in claim 1, wherein therear portion extends beyond the trailing edge of the fixed wing and wingtip device.
 3. An aircraft as claimed in claim 1, wherein the rearportion of the fairing comprises a trailing edge which is parallel indirection to the trailing edge of the fixed wing and/or wing tip device.4. An aircraft as claimed in claim 1, wherein the rear portion tapers inspan-wise width as it extends away from the trailing edge of the fixedwing and wing tip device.
 5. An aircraft as claimed in claim 1, whereinthe rear portion comprises a point of inflection in the line of flightdirection, at which point the cross-sectional profile of the rearportion changes from a convex profile to a concave profile, as the rearportion extends in a rearward direction.
 6. An aircraft as claimed inclaim 5, wherein the point of inflection is located in a region aroundthe 100%, 90%, 80%, 70%, or 60% of the chord length of the wing, takenin a line of flight direction and moving from the leading edge (0%) totrailing edge (100%) of the wing.
 7. An aircraft as claimed in claim 1,wherein as the fairing extends in a span-wise direction, the rearportion of the fairing comprises a surface which extends tangentiallyfrom the wing skin of the fixed wing in a concave direction, undergoes apoint of inflection to extend in a convex direction, and undergoes afurther point of inflection such that it extends in a concave directionto a point where it is tangential to the wing skin of the wing tipdevice.
 8. An aircraft as claimed in claim 1, wherein the fairingcomprises a front portion blended into and extending rearwardly from theleading edge of the fixed wing and the wing tip device when the wing tipdevice is in the flight configuration.
 9. An aircraft as claimed inclaim 8, wherein the front portion of the fairing meets the leading edgeof the fixed wing and wing tip device in a tangential direction.
 10. Anaircraft as claimed in claim 8, wherein the front portion of the fairingmeets the leading edge of the fixed wing and wing tip device, such thatwhen viewed in a line of flight cross-section, there is substantially nodiscontinuity between the fairing and the leading edge of the fixed wingand wing tip device.
 11. An aircraft as claimed in claim 8, wherein asthe fairing extends in a span-wise direction across the wing, thefairing comprises a concave surface extending from the wing skin of thefixed wing, the concave surface starting in a direction tangential tothe wing skin, a point of inflection in a span-wise direction, at whichpoint the surface becomes a convex surface, such that the convex surfaceextends over maximum protrusion of the hinge arrangement, an additionalpoint of inflection, at which point the surface becomes a concavesurface, such that the concave surface meets the wing tip device wingskin in a tangential direction.
 12. An aircraft as claimed in claim 1,wherein the fairing is substantially symmetrical about a line of flightaxis, the axis located at the point of greatest depth of the fairing.13. An aircraft as claimed in claim 1, wherein the edges of the fairing,where the fairing blends into the fixed wing or wing tip device, theedges extend in a line of flight direction.
 14. An aircraft as claimedin claim 1, wherein the fairing comprises a consistent span-wise widthacross at least 70%, 80%, 90% or 100% of the fairing.
 15. An aircraft asclaimed in claim 1, wherein the hinge arrangement extends in a line offlight direction.
 16. An aircraft as claimed in claim 15, wherein thehinge arrangement extends in a line of flight direction such that itextends over at least 60%, at least 70%, at least 80%, or at least 90%of the aircraft wing in a line flight direction
 17. An aircraft asclaimed in claim 1, wherein the fairing is located on the lower surfaceof the aircraft wing.
 18. An aircraft wing comprising a fixed wing and awing tip device at the tip thereof, wherein the wing tip device isconfigurable between: (i) a flight configuration for use during flightand (ii) a ground configuration for use during ground-based operations,in which ground configuration the wing tip device is moved away from theflight configuration such that the span of the aircraft wing is reduced,the aircraft wing further comprising a hinge arrangement connecting thefixed wing and the wing tip device, wherein the hinge arrangementprotrudes beyond an outer surface of the fixed wing and wing tip device,and a fairing covering the protruding portion of the hinge, wherein inthe flight configuration the fairing comprises a rear portion with aconcave surface, the surface creating a lift-generating portion of thefairing during flight.
 19. An aircraft comprising an aerodynamicstructure, a protruding structure and a fairing covering the protrudingstructure, wherein the fairing is blended into the aerodynamic structurein a line of flight direction and in a span-wise direction, such thatthere are no discontinuities at the transition between the surface ofthe aerodynamic structure and the fairing.
 20. An aircraft comprising anaerodynamic structure according to claim 19, wherein the fairing meetsthe surface of the aerodynamic structure along an interface, and whereinthe fairing is shaped such that the surface of the fairing is tangentialto the surface of the aerodynamic structure along the interface.
 21. Afairing for an aircraft, the fairing comprising an interface surface forinterfacing with the aircraft in a tangential direction, and anaerodynamic surface, the fairing further comprising a seamlesstransition from the interface surface to the aerodynamic surface.
 22. Afairing as claimed in claim 21, the fairing comprising a longitudinalaxis corresponding to the line of flight direction when mounted on anaircraft, wherein the cross-sectional profile of the fairing takenperpendicular to the longitudinal axis comprises a bell-shaped curve.23. A fairing as claimed in claim 22, wherein the aerodynamic surfacecomprises a concave surface.